On this page: https://stackoverflow.com/questions/new/haskell?show=all&sort=newest, control+clicking the new, popular and need answers tabs opens the pages in the same tab instead of in a new tab. In the past this problem did not exist.
I believe this has something to do with the way current Stack Overflow's on-page on-click activity is handled under the new-nav. As pointed out by ShadowWizard in the comment:
This is due to new navigation, you can opt out while it is still in beta. (hence naturally got lots of bugs)
Yes, this behavior is due to the recent changes (this problem did not exist when I was on the old nav) made in the new-nav where the AJAX (as per Patrick Hofman's comment below) call handles on-click (ctrl-click or cmd-click in case of Mac) on the tab links to open in.
Unfortunately, I am on Mac OS so here is what I did. I installed a "Command-Click Fix" Chrome extension. This extension makes Command-Click open a new tab on pages that don't do it properly. Make sure to reload/refresh the webpage after installing the extension. Now, using cmd+click on the tab links works perfectly i.e. opens the link in a new browser tab.
The above test was performed in the Chrome Version 43.0.2357.134 (64-bit). I can reproduce this on the other two browsers i.e. Firefox (Version 39.0) and Safari (Version 8.0.7 (10600.7.12))
I am using MacBook Pro (Retina, Late 2013; OS X Yosemite Version 10.10.2).